This round slider rule is marked ALRO Syst 200R, comes in it’s complete metal case. Made in Holland in The Hague somewhere after the second world war in the 1950’s. It has the patent (pending) numbers in the centre. It has a light aluminum case with brass studs in the middle and plastic centre cursor. It is in good working condition with signs of use and age (decal in case is a bit wobbly). Closed it measures ca 13,5 cm or 5 3/8 inches wide. See pictures for details.
Check the video on how to work your vintage man tool : slide rule operation instructions!
